Anomalous resistive switching in memristors based on two-dimensional palladium diselenide using heterophase grain boundaries

The implementation of memristive synapses in neuromorphic computing is hindered by the limited reproducibility and high energy consumption of the switching behaviour of the devices. Typical filament-type memristors suffer, in particular, from temporal and spatial variation in the set voltage and resistance states due to stochastic filament formation. Here, we report memristors based on two-dimensional pentagonal palladium diselenide (PdSe2) that can exhibit anomalous resistive switching behaviour with two interchangeable reset modes: total reset and quasi-reset. Heterophase grain boundaries are formed in the PdSe2 via local phase transitions induced by electron-beam irradiation, which leads to residual filaments along the grain boundaries that can guide the formation of conductive filaments. When operated in the quasi-reset mode, the memristors show a sixfold improvement in switching variation compared with devices operating in the total-reset mode, as well as a low set voltage (0.6 V), long retention times and programmable multilevel resistance states. We also show that the devices can emulate synaptic plasticity and that multipattern memorization can be implemented using a crossbar array architecture. Heterophase grain boundaries in memristors based on pentagonal palladium diselenide can guide the formation of conductive filaments during resistive switching, leading to devices with uniform switching properties, low set voltages, long retention times and programmable multilevel resistance states.